This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/HR98/00004 which has an international filing date of Jun. 17, 1998, which designated the United States of America.
The invention pertains to the area of bone reconstruction in orthopaedic surgery and traumatology and it will find its application in the management of xe2x80x9cpseudoarthrosis defectsxe2x80x9d in which a bone fragment is missing due to a bone defect. The bone fragment must be replaced by a transplant in order to facilitate a successful healing process. Such bone defects are usually consequences of a major trauma (for example gunshot wounds). They are also seen in open fractures for which a surgical procedure is required to remove a destroyed bone fragment, also following infections (osteomyelitis), requiring the removal of bone sequesters, and finally after the removal of bone tumours or cysts. Besides the aforementioned xe2x80x9cpseudoarthrosis defectxe2x80x9d, the area also encompasses the so called xe2x80x9cavascular pseudoarthrosesxe2x80x9d in which there is a lack of viable bone cells in the area of the fracture as a result of bone devascularisation due to a radical surgical procedure, so that the healing process falls to occur (although the bone edges may be in contact). That is why a method of osteoinduction, including autologous bone transplant is also applied for these cases.
The purpose of a bone transplant is of two kinds:
1. It represents a medium for the appositional growth of bone cells from the edges of a bone defect. For this reason, and owing to its faster revascularisation, a spongy structure is more suitable than the homogenous one.
2. A transplant should have the local osteoinductive effect, which can only be found in a viable tissue contaning the living bone cells (osteoblast) which generate a new bone by the secretion of osteoidxe2x80x94protein into which calcium hydroxyapatit is deposited, thus forming a mineral, solid inorganic part of the bone.
The basic technical problem is how to obtain a transplant of a highest possible quality (with the highest degree of viability), which will produce strong osteoinduction using the effect of the living transplanted cells (osteoblast cells). In addition the above mentioned transplant, the bone morphogenic protein induction method, using the bone morphogenic protein (BMP) extracted from the ox-bone, is becoming increasingly more popular. Some other methods, involving locally altered growth factors, are currently in the stage of experimental research work. Although none of these cells are the living cells, BMP placed locally into the traumatised area stimulates the growth of the neighbouring cells and induces more intensive bone formation.
In my previous patent application submitted to the State Office for Intellectual Property on Oct. 9, 1997, the reference number P970539A, I presented the static and dynamical method of the mechanical induction of the periosteal reactive bone growth. The former method is the one using conus screws with a self-tapping tip which provides for a much simpler procedure, since its application does not require any subsequent stimulation. It has been found that the optimum result is achieved by a wedge-shaped screw placed at an angle of 7xc2x0. However, the width of the upper part of the opening corresponds only to the diameter of initial part of the screw. The latter gradually widens so that the final diameter of the upper part of the screw is over 0.5 mm bigger than the diameter of the its diameter at the entry. Thus, as it keeps penetrating deeper into the bone, the screw behaves as a wedge which overstrains the bone and pushes it laterally. This results in an osseous reaction, induced during the period of 4 to 8 weeks on the surfaces around the screw. These newly ossified surfaces are then removed by a chisel and transferred to the operative field in the area of the bone defect.
The methods for the surgical management of bone defect involve free bone transplants, the Ilizarov method of segment transplantation and microsurgical vascularised bone transplant. Free bone transplants methods are the most numerous, the simplest for application and therefore the most widely used ones. They comprise:
1. Autologous spongioplasty (the recipient""s own cancellous bonexe2x80x94red bone marrow) which is widely accepted as the best osteoinduction material since it contains its own viable cells, and is of a spongy structure. It is usually taken from the pelvis (crista iliaca).
2. Corticospongioplastyxe2x80x94besides the internal, spongy part of the bone, this method also uses the external, solid, cortical part of the bone. The cortical part itself is less valuable as an osteoinduction medium, since it contains a low osteoblast count, and by its structure it is a homogenous, solid bone (which becomes dead after the transplantation), so that at a later stage it has to be totally turnovered by new cells from the neighbouring bone tissue. However, its advantage lies in the fact that it has very good mechanical hardness. It is usually taken from the pelvis area or from the medium third of the fibula.
3. Homologous spongioplasty (human cancerous bone taken from a bone bank) is being abandoned (AIDS, hepatitis, reaction to foreign proteins, infection etc.) and is being replaced by the use of artificial osseous tranplants.
4. Transplantation of an artificial bone. This method is gaining in popularity owing to its major advantage which lies in the fact that the transplanted tissue is not the recipient""s own bone, which reduces the surgical trauma sustained by the recipient. A shortcoming of this method lies in the fact that these transplants do not contain viable cells, but they serve as a spongy medium for the implantation of the neigbouring cells, so that the healing process is much slower and of a much lower quality than with the application of autologous spongioplasty. This group consists of two types of transplants. The first group are the transplants originating from biological tissue (bovine spongiosis, collagen, collar minerals and so on). The second group is relative to transplants of inorganic origin (hydroxiapatit). Many of these are protected under different names such as Bio-Oss(copyright) (Geistlich AG, Switzerland), Osteovit(copyright) (B. Braun Melsungen AG), and others.
5. Decortication of Judet (M. E. Mueller and all, Manual of Internal Fixation, Springer-Verlag, Third Ed. 1991,720).
6. BMP (bone morphogenic protein) osteoinduction (OP-1(trademark) striker(copyright) BIOTECH).
7. Periosteum transplantation is mentioned only sporadically in literature and it is described in all insignificant number of cases. It is not widely used due to the uncertainty regarding the subsequent bone formation, i.e. due to a much higher degree of efficiency and safety of the previously mentioned methods.
8. Reactive Cambiplasty by means of a conical screw induces periosteal reaction which is then used as an periosteal autologous bone transplant (P970539A).
The second group of operative methods for the surgical management of bone defects consists of the segment transport according to Ilizarov and a microsurgical method involving the transplantation of a vascularised bone transplant. However, these two methods differ significantly from the previously described ones since they do not involve a free bone transplant so no comparison is possible between them.
And finally, it should be pointed out that the method of autologous spongioplasty is until now considered to be the best osteoinduction method. This has been corroborated by many scientific research results. Due to the simplicity of its application, this method is also the most widely used one.
The essence of the invention is based on the scientifically proven fact. First presentation of the Adoptive periosteal cambiplasty method and differential conical screw was a IV European FECAVA/SCIVAC Congress, Bologna, Italy Jun. 18-21 1998. Second presentation was at XXIII World WSAVA Congress, Buenos Aires, Argentina Oct. 5-9 1998. That the recipient""s own mechanically induced periosteal reaction on the bone surface after 4 to 8 weeks shows a substantially higher (even twice as high) osteoinduction potential than the recipient""s own cancellous bone (red bone marrow).
It should be emphasised at this point that for two reasons this reaction cannot be mistaken for a common periosteal callus which appears in fractures. These reasons are as follows:
1. The reaction occurs as an adjustment to a new strain in the bone, and not as a reaction to a trauma. The induction of growth of new osseous cells (osteoblasts) is a result of turnover resulting from altered, intentionally induced and increased internal strain which occurs in an otherwise healthy bone with an uninterrupted osseous continuity, rather than as a sequeala of a fracture and part of its natural healing process.
2. Histologically, the only tissue present is the bone tissue, whereas the tissue of a fracture callus is mixed with the adjacent callus from the haematoma, the endosteal part and the muscle. We may even come across cartilage fragments. This difference is evident microscopically and may be proven in a number of ways.
The above mentioned method was referred to as xe2x80x9ccambiplastica reactivaxe2x80x9d in my previous patent application since this name provides for the anatomical definition of the method and thus distinguishes it from periosteal transplantation. Periosteum consists of two layers, the external fibrous layer which contains blood vessels and capillaries, and the internal, cambial layer which contains a very thin layer of the so called osteoprogenitor cells, the antecedents of osteoblasts. By some atoms it contains, this layer does not belong to the periosteum but rather to the bone, which is to a certain extent corroborated by my research. As has been said already, neither the periosteum nor the cambial layer are transplanted. The method consists of the surgically induced mechanical changes to the internal strain which, in turn, induce the reaction within the cambial layer. After 4 to 8 weeks, the quantity of the reaction, i.e. of the newly-formed bone, is sufficient for transplantation into another part of the body where there is a lack of bone tissue or where osteoinduction is required (for example atrophic pseuodarthrosis or prolonged osseous healing, etc.).
This delayed transplantation of the osseous tissue generated by previous mechanical stimulation is a novelty and the essence of the invention. Therefrom the name xe2x80x9creactive Cambiplastyxe2x80x9d rather than only cambiplasty. Cambiplasty as such does not exist. If it did, it would fall under the category of periosteum transplantation. In this procedure, the periosteum chiselled from the surface of the bone would contain a part of the cambial layer. However, in this stage (without prior mechanical stimulation), this is a microscopical layer of the soft tissue, rather than of a solid bone (of a slightly spongy consistence) as a reaction in the xe2x80x9creactive cambiplastyxe2x80x9d. Moreover, it has already been said that the method of periosteal transplantation is not widely accepted due to the uncertainty of its results.
My subsequent scientific research resulted in some new notions and, consequntly, in the change of the definition of the previously described cambial reaction. This, in turn, has resulted in the change of the method""s name, which is now called xe2x80x9cadaptive periosteal cambiplastyxe2x80x9d. The term xe2x80x9cadaptivexe2x80x9d refers to the adaptation of the bone to a new strain, and is not restricted to the description of a periosteal reaction. The term periosteal closely describes the area involved, and cambiplasty refers to the part which is being transplanted. The essence of this invention is the improved mechanical action of the differential conical screw (FIG. 3) as opposed to the effect of the conical screw described in my previous patent application, reference No. P970539A. The screw is not placed in the previously threaded conical hole, but rather into a straight hole in the bone, most commonly through a single corticalis in the area of the tibial diaphysis. In this hole a thread of the same pitch and diameter as the lower, cylindrical part of the screw, is made by a thread cutting tap. The pitches of the thread may be between 0.3 and 2 mm. During the twisting of the differential conical screw into the bone, its conical shape induces distractional radial forces around the screw in the bone. These forces tend to be stronger in the surface parts of the bone owing to the conical shape of the screw. This difference in the stressxe2x80x94strain distribution of the radial forces in the surface and deep layers of the bone constitutes the main difference between the effect of this differential conical screw and the effect of the simple conical screw described in my previous application. Conical (wedge) angle of the screw may vary between 1xc2x0 and 10xc2x0. Optimal angle is about 7xc2x0 or halfangle of 3.5xc2x0 (FIG. 3).
The second difference is contained in the term xe2x80x9cdifferentialxe2x80x9d, which is a word referring to the function of the screw and implying the kinematics of the twisting of this screw into the hole in the bone. Besides the conical shape, this screw also features a variable thread pitch in its cone part, which increases gradually from its lower, cylindrical part, to its head. This increase is continuous and incremental at each thread, and may vary between 0.01 and 0.1 mm per thread. This variability of the screw pitch is typical of this particular screw shape resulting in the above mentioned differential function, which is made possible by the differences in thread pitches, which are shorter and prethreaded in the osseous part. For this reason, the twisting of such a screw into the cylindrical hole in the bone, which features the prethreaded screw pitches, corresponding to the pitches in the cylindrical part of the screw, starts as a normal procedure, but later on, after 2 to 5 threads, as the screw penetrates deeper into the bone, it induces distraction forces and sressxe2x80x94strain distributions which are axial to the axis of the screw. This bone extension provides for additional stimulation and is conducive to the above mentioned adaptation reaction appearing on the bone surface, which in turn results in the generation of the future autologous bone transplant. The screws need be produced from common implant materialsxe2x80x94stainless steel ISO 5832/6 or 5832/IV or 5832-8 or from a titanium alloy for ISO 5832-3.